18 



MASS. EXPERIMENT STATION BULLETIN 429 



Table 9. — Eggs Laid and Days of Laying During Annual Molt, 

 Production Stock Only, 1938-1944. 



Complete Wing Molt Incomplete Wing Molt 



Feather Region 



Number Average Average 



of Number Number 



Birds of Eggs of Days 



Laid Laying 



Neck (Cervical) 135 28.8 53.6 



Breast (Pectoral) 98 9.4 20.8 



Thigh (Femoral) 135 10.0 22.9 



Lower Leg (Tibial) 134 5.2 12.9 



Back (Dorsal) 135 21.8 41.8 



Wing Primaries 135 29.9 71.9 



Persistency in Relation to Wing Molt. — The seven generations of females 

 bred for high fecundity have been combined into two groups: those in which 

 molt was complete by the end of December and those that had not completed 

 the molt on that date. The two groups are compared in table 10. 



Table 10. — Persistency and Wing Molt, Production Stock Only, 1938-1944. 



Complete 

 Wing Molt 



Number 



of 



Birds 



Average 



Incomplete 

 Wing Molt 



Number 



of Average 

 Birds 



Length of biological year, days 135 360.2 138 378.9 



Production during biological year, eggs 135 228.0 138 241.0 



Annual production, eggs 135 222.1 142 229.4 



Number of primaries shed when laying stopped.. 135 3.8 138 3.3 



Date of completing wing molt 135 Dec. 6 138 - 



Date of termination of biological year 135 Sept. 27 138 Oct. 20 



Birds with incomplete wing molt by the end of December had a biological 

 laying year about 19 days longer than birds that had completed the wing molt 

 by that date. These later molting birds had a mean laying period of about 379 

 days from their first pullet egg to the cessation of production associated with 

 annual molt. 



Egg production during the biological year differed significantly in the two 

 groups. The birds completing wing molt by the end of December averaged to 

 lay 23 fewer eggs than those completing wing molt after December. 



The number of eggs laid in a 365-day laying year was also slightly higher in 

 the late-molting group. It should be noted, however, that even the birds com- 

 pleting wing molt in December can scarcely be considered as molting earlj^ 



The earlier molting group averaged slightly higher than the later molting 

 group in number of primary wing feathers molted when laying stopped, but the 

 difference is of doubtful significance. The data as a whole indicate that these 

 birds bred for high persistency do possess the ability to lay when the annual molt 

 is well advanced. 



December 6 was the average date when wing molt was completed in the earlier 

 molting group. For the later group, the date of completion was well into January. 



